Two suggestions:
a) Multiple Rails processes behind a load-balancing reverse proxy.
b) Run the blocking task in the background and provide a way for the browser to refresh status (for example, timed refresh of status div via javascript):
http://www.yup.com/articles/2006/05/23/ handling-rails-background-and-batch-jobs-with-backgrounddrb http://backgroundrb.rubyforge.org/
